ERBB2 and cancer: Systemic therapies include chemotherapy, endocrine therapy (for hormone receptor-positive tumors), anti-HER2 therapy (for HER2-positive disease), bone-stabilizing agents, poly(ADP-ribose) polymerase (PARP) inhibitors (for cancers with specific DNA-repair defects, including BRCA mutation carriers), and, more recently, immunotherapy [40,51,52,53].